The use of absorbent materials, particularly absorbent polysaccharide materials, at the wound-contacting surface of wound dressings is known. Dressings comprising alginate fibres are described, for example, in GB-A-1394742, GB-A-2103993, U.S. Pat. No. 4,421,583, EP-A-227955, EP-A-236104, EP-A-243069 and WO-89/12471. GB-A-1329693 describes a dressing comprising a substrate bearing a haemostatic material comprising an alginate and a water-soluble polymer such as sodium carboxymethyl cellulose.
U.S. Pat. No. 3,731,686 describes an absorbent dressing including a compressed body comprised of absorbent fibres of an alkali metal salt of carboxyalkyl cellulose having an average degree of substitution greater than 0.35 carboxyalkyl radicals per anhydroglucose residue, said absorbent fibres of an alkali metal salt of carboxyalkyl cellulose being heat-treated so as to become insoluble but swellable in water at room temperature. The dressing is typically a tampon, sanitary napkin or diaper having a core of the compressed absorbent fibres. U.S. Pat. No. 3,589,364 relates to bibulous water-insoluble cellulosic fibres which retain the fibrous form of the original cellulose raw material and are prepared by wet-crosslinking fibres of a water-soluble carboxymethyl cellulose salt. The fibres are suggested for use in a tampon, surgical dressing, surgical sponge, catamenial napkin or diaper. U.S. Pat. No. 4,634,438 and U.S. Pat. No. 4,634,439 describe a hygienic pH-regulating product for topical application, particularly a catamenial device, comprising a homogeneous mass of carboxyalkyl-modified cellulose fibres of degree of substitution 0.01 to 0.30 wherein the carboxyalkyl groups are in the free acid form.
Wound dressings containing a water-absorbent polymer such as sodium carboxymethyl cellulose are described in GB-A-1548678 and EP-A-92999 and in the books "Wound Management and Dressings" by S. Thomas (The Pharmaceutical Press) at pages 55-61 and "Advances in Wound Management" edited by T. D. Turner et. al (J. Wiley) at pages 89-95, and in the article by S. Thomas in J. Wound Care, Vol. 1 (1992) No. 2, pages 27-30. These dressings, generally known as hydrocolloid dressings, contain the water-absorbent polymer in powder form in an elastomeric and/or adhesive matrix such as polyisobutylene; the resulting material forms the wound-contacting layer of the hydrocolloid dressing. The hydrocolloid dressing takes up wound fluid to form a gel that produces a moist environment which facilitates healing. The absorbent component of the dressing is also produced in the form of granules or paste for the treatment of small cavities.